"We are facing a very serious concern. We've never had a foreign adversarial power be already involved in our electoral process with the DNC hacks. We've never had a nominee of one of our major parties urging the Russians to hack more," Clinton told reporters travelling with her on her new campaign plane.

When pressed about whether she believed the Russians were actively trying to elect Trump to the Oval Office, Clinton took a long pause before responding. "I think its quite intriguing that this activity has happened around the time Trump became the nominee," she conceded.

"I think it's quite intriguing that this activity has happened around the time [Donald] Trump became the nominee. And look, he very early on allied himself with [Russian President Vladimir] Putin's policies," she alleged.

Some US media outlets have reported the American intelligence agencies are investigating potential Russian interference in US elections. This was first reported by The Washington Post. She described this as a credible report.

The investigation is being coordinated by the US director of national intelligence, the daily said. This shows that the US need to be "on guard to protect our electoral system at all levels and we have to make it clear that we're not gonna let anyone interfere with decisions of the American people," Clinton said.

"The fact that our intelligence professionals are now studying this, and taking it seriously raises some grave questions about potential Russian interference with our electoral process," she said.